As a contributing author of the bookWe Are One: A Celebration of Tribal Peoples, published in late 2009,[36] which examines the culture of peoples around the world, he explores global diversities and threats facing humankind. Among other contributors are several western writers, such as Laurens van der Post, Noam Chomsky, Claude Lévi-Strauss and also indigenous peoples, such as Davi Kopenawa Yanomami and Roy Sesana. The book is composed of a collection of photographs, statements from tribal people, and essays from international authors, politicians, philosophers, poets, artists, journalists, anthropologists, environmentalists and photojournalists. In his essay, Goldsmith talks about how his travel through the world in his youth gave him first-hand experience of the misery brought by the promise of western "progress" and "development". He reflects on the culture of these people and, in reverence to it, urges people in the modern world to question what "progress" can really mean.[37] The royalties from the sale of this book go to the indigenous rights organization, Survival International.

The report's[40] recommendations included increased taxes on short-haul flights and highly polluting vehicles, with the proceeds being used to cut the cost of clean alternatives; rebates on Stamp Duty and Council Tax for people who improve the energy efficiency of their home; and in addition it proposed a moratorium on airport expansions.[41]

In 2008, Goldsmith was alleged to have breached electoral rules by making a donation of £7,000 to his Party while not on the electoral register. Commenting on the issue, Goldsmith explained: "everything has been declared on time and accurately; however, for a few weeks last year I was not on the Electoral Roll, my name having been removed from Kensington and Chelsea's voter list, given that I was in the process of signing up for Richmond. Whatever was donated in that time may have to be repaid, but there is no suggestion that anything other was improprietous".[47]

In late 2009, the press asserted that Goldsmith had non-domiciled status and that as a Londonresident, albeit a discretionary beneficiary, he has use of British properties through a trust set up by his late father.[48] Goldsmith responded, in a statement about the suggestion of tax avoidance, that he has "always chosen to be tax resident in the UK" and virtually all his income was paid to into British banks. Of non-dom status as a result of his late father's international status, Goldsmith added that he had already instructed his accountants to relinquish it of his own volition by early 2009, so as to avoid being quizzed by any newspapers.[49][50]

Goldsmith was returned as Member of Parliament for Richmond Park on 7 May 2015, increasing his majority from 4,091 to 23,015 votes. He also achieved an increase of 8.5 percent of the share of the vote from the 2010 election, receiving a total of 58.2 percent of all votes cast by his constituents. This was the biggest increase in majority of any MP at the UK 2015 general election.[51]

Channel 4 News raised questions over Goldsmith's declared expenses at the 2010 election, arguing "our findings do suggest that Zac Goldsmith has questions to answer about whether his spending has complied with both the letter and spirit of the law". Goldsmith denied any wrongdoing and countered by stating that Channel 4 engaged in sleazy unethical journalism.[52][53]The Bureau of Investigative Journalism complained to the Electoral Commission over the report about Goldsmith's expenses,[54] who ruled that Goldsmith had not intentionally or unintentionally broken any rules.[55][56]

On 15 July 2010, Goldsmith appeared in a live interview on Channel 4 News to answer questions over his election expenses.[57][58] Goldsmith spent the first six minutes arguing about the details of when and how he had been asked to appear. Jon Snow said Goldsmith gave a "travesty of the truth"[58] on that matter and that he was "prevaricating" and running them out of time. Goldsmith retorted by accusing Snow of being a "charlatan". Snow dared Goldsmith take the matter to OFCOM. Goldsmith did so[59] but his specific complaint was rejected.[58]

Snow raised two questions about his expenses. The first was about signs: "You expended £2,800 on 600 signs but £262 is what you said you spent when you told the Electoral Commission on your return". The response was "The formula we used is exactly the same formula ... as used by MPs and candidates around the country. Every decision we took was approved by electoral experts at Conservative Central Office". Snow said they were investigating 30 MPs and in terms of scale, Goldsmith's expenses far outstripped the others. The claim was reduced because the signs had been allocated to the local election budget. It was debated whether signs that said "Vote Zac Goldsmith" and "Vote Conservative" could be charged to the election budget for a local election candidate when that other candidate was not mentioned on the sign. The response was that it had been "checked" and that was "standard practice" across the country. The second question was about jackets with "I back Zac" stickers on the back. "They cost £2,168 but you only said you paid (spent) £170". The response was that the stickers cost £170 and the jackets had not been customised for the Zac Goldsmith campaign. "They are off the shelf. Look at them", Goldsmith responded further, adding that they were generic jackets and will be used in other election campaigns.[60]

Channel 4 News presented their case online including scans of the spending documents.[61] Goldsmith has posted a response on his blog.[62] The interview itself became a news item.[63] On 21 July 2010, the Electoral Commission announced that, following their initial 5-day assessment, they have decided to upgrade the investigation to the status of "case under review"[64] and that they will make enquiries "in order to establish the facts of the matter".[65] The Commission reported in December 2010: they decided there was no further case to answer and that there was no intentional rule-breaking but they did observe that the cost-sharing between general election and local elections contests was "not consistent with the Commission's guidance or good practice", that the submission was "unclear in places" and the Goldsmith's campaign may have overspent by £966 in the short campaign.[55][56]

An enthusiastic advocate of direct democracy, such as Switzerland's model of using referendums, Goldsmith believes it would help combat feelings of disenfranchisement among people and increase accountability.[66] Among his key interests is education; in an interview with Fairtradefashion designersPeople Tree, he said "I've put a big emphasis on schools. One campaign is to ensure every school [is] fitted with a proper kitchen that can double up as a classroom. Children need to know where their food comes from and how to cook it. We're also trying to help every school source its food sustainably and locally".[67]

On a local level Goldsmith has been involved in campaigns within his constituency of Richmond Park, in matters such as schools, hospitals and recreation areas.

In 2007, he opposed the opening of a superstore by supermarket chain Sainsbury's in Barnes. He spearheaded a referendum conducted by the Electoral Reform Society to poll local residents on the issue, working closely with a local campaign group. With a turnout of 61.6%, more than 4,000 residents, who made up 85% of the votes cast, came forward to oppose the construction of the store at White Hart Lane. Sainsbury's ultimately opened the branch after revising its planning application.[68][69]

In November 2002, Goldsmith helped establish FARM, a campaigning organisation for British farmers.[84] Goldsmith also funded the Organic Targets Bill Campaign to promote organic farming in 1999.[85] He is a longstanding donor to the Soil Association. In 2007, he was a participant at the Soil Association Annual Conference, during which he competed in an organic fashion show on 25 January[86] and afterwards debating on a Question Time panel on 27 January.[87]

Goldsmith was married for ten years to Sheherazade Ventura-Bentley with whom he has three children: two daughters, Uma Romaine and Thyra, and a son, James.[91] The couple married on 5 June 1999, in a ceremony at St Simon Zelotes Church in Chelsea followed by a reception at The Ritz Hotel.[92] The Goldsmith couple separated in April 2009,[93] and received a decree nisi on 10 May 2010 after an "admission of adultery".[93][94][95] Sheherazade and Zac Goldsmith were featured in Vanity Fair's 67th Annual International Best-Dressed List among "Best-Dressed Couples".[96] Goldsmith revealed, in 2000, that he wore recycled Savile Row suits which had belonged to his late father.[14]